This invention is concerned with assuring the hermetic sealing of high reliability batteries such as those used for military purposes or medical purposes. Such batteries are generally relatively small and of high energy density. The contents of such batteries typically may consist of high energy corrosive materials such as lithium anodes, carbon current collectors and liquid thionyl chloride cathode/electrolytes and the like. Other such batteries may include lithium anodes, organic solvent electrolytes such as propylene carbonate containing a dissolved salt such as lithium perchlorate for enhanced conductivity and solid cathode materials such as manganese dioxide, vanadium pentoxide or carbon monofluoride. Another such battery is one having a cathode depolarizer material such as an organic-iodine charge transfer complex compound.
Such batteries are usually encapsulated in a metal container having a fill port. Stainless steel is the metal most commonly used. Following placement of mechanical parts and any solid chemical constituents in the container, the container is then filled with any liquid or liquid-like battery constituents, such as fluid cathode/electrolytes in the case of thionyl chloride batteries or molten charge transfer complex in the case of the iodine batteries, by pouring same into the battery through the fill port. The fill-port is then sealed.
The hermeticity or perfection of seal at the fill port is an important feature in high reliability cells. It is also important that the seal be amenable to testing in order to ascertain and demonstrate that a high degree of hermeticity has been achieved.